import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int m = sc.nextInt();
        Area[] areas = new Area[m];
        for (int i = 0; i < m; i++) {
            areas[i] = new Area(sc.nextInt(), sc.nextInt());
        }
        Arrays.sort(areas);
        TreeSet<Integer> zeros = new TreeSet<>();
        for (Area a : areas) {
            Integer key = zeros.ceiling(a.left);
            if (key == null || key > a.right) {
                zeros.add(a.right);
            }
        }
        System.out.println(n - zeros.size());
    }
    
    static class Area implements Comparable<Area> {
        int left;
        int right;
        
        public Area(int left, int right) {
            this.left = left;
            this.right = right;
        }
        
        public int compareTo(Area another) {
            return right - another.right;
        }
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public String nextLine() throws Exception {
        return br.readLine();
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}